Is it legal to throw with your contact/pivot foot slightly to either side of the marker? I've been told through less than reputable sources that having so much as a pinkie toe in line with the marker counts as a legal shot.

The rule is that you must have a point of contact on the line between the centre of the pole and the centre of the marker, up to 30cm behind it. It could be your finger, your nose or whatever else you chose, but it must be behind the centre of the marker...

Keep in mind that the rules do not say that the center of your point of contact must be behind the center of your mini. So your irreputable sources would be correct in saying that as long as you have so much as a pinkie toe behind the center of your mini, your stance would be legal.